These Theewaterskloof Dam facts and key statistics cover the history, engineering and sheer scale of the dam that Theewater Sports Club calls home – the water we sail, ski, paddle and fish on.
Theewaterskloof Dam – The largest dam in the Western Cape, officially completed and opened on the 24 April 1982, is a crucial reservoir for Cape Town and provides water for farmers during the dry months.
The concept of a storage dam started way back in 1952, after serious drought was experienced in the Western Cape, in 1964 the area for such a dam was identified. It would become known as the Riviersonderend Berg River Scheme.
This project was described as: ‘one of the most impressive civil engineering projects of the 1980’s‘
The Theewaterskloof dam is linked to Franschhoek’s Berg River dam by an 18km tunnel through the Franshhoek mountains. Both dams get their water from the Franschhoek mountains. A very interesting fact about the tunnel system, is that water can be transported both ways through the tunnel. If the Berg River dam has excess water, water can be diverted to the Theewaterskloof dam and visa versa.
More interesting facts about the dam:
Theewaterskloof dam is a conventional earthfill dam
The dam has a capacity of 483 million cubic metres of water when full.
When full, the water covers an area of 5 100 ha
The height above the lowest foundation: 37,5m
Spillway capacity: 390 m3/s
The Franschhoek tunnel is a reinforced concrete tunnel, it is 4,3m-diameter
The distance of the tunnel is 7,9km
The Riviersonderend–Berg River transfer scheme
Theewaterskloof Dam is the 7th biggest dam in South Africa (the Gariep Dam is the biggest). It was built as the central storage unit of the Riviersonderend–Berg River transfer scheme, one of the most imaginative water transfer schemes in the country, which links the Berg and Sonderend rivers in the Western Cape. The tunnel through the Franschhoek mountain was the second phase, followed by the construction of the Jonkershoek tunnels.
The Jonkershoek tunnel system includes a total of 23 km of tunnels, built with 236 000 m³ of concrete. The main Jonkershoek tunnel cuts through the Groot Drakenstein and Jonkershoek mountains for 13 km, surfacing at the Kleinplaas Dam into the Eerste River in the Jonkershoek valley.
More key statistics
- Crest length: 646 m
- Type of spillway: side-channel
- Franschhoek tunnel: runs 7,9 km from the Villiersdorp side to the Berg River valley
Facts and figures from the construction
- If all the holes drilled for blasting on the Riviersonderend–Berg River project were joined into one continuous hole, it would stretch roughly 2 300 km.
- The 470 000 m³ of concrete cast on the project was only 40% of that used to build the Vanderkloof Dam.
- Measured in 50 kg pockets, 3,4 million pockets of cement went into the various constructions on the project.
- If all the soil and rock excavated were piled on an area the size of a rugby field, the dump would be 12 storeys high.
- One and a half million kilograms of dynamite were used for blasting on the project.
Source: DWS, ‘Blood, Sweat and Tears at Riviersonderend’, compiled by Lani van Vuuren.
